Suggest an editImprove this articleRefine the answer for “What is "Test Driven Development (TDD)"?”. Your changes go to moderation before they’re published.Approval requiredContentWhat you’re changing🇺🇸EN🇺🇦UAPreviewTitle (EN)Short answer (EN)**Test Driven Development (TDD)** is a development approach in which tests are written first and the working code only after: the developer formulates the expected behavior as unit tests, then writes the minimal implementation to make them pass. **Key point:** the TDD cycle (Red, Green, Refactor) repeats continuously and delivers safe refactoring plus a clean, modular architecture.Shown above the full answer for quick recall.Answer (EN)Image**Test Driven Development (TDD)** is a development approach in which **tests are written first, and only then - the working code**. The logic is simple: the developer first formulates the expected behavior of a function as unit tests, and only then writes the minimal implementation needed to make the tests pass. --- ### **What TDD is, in simple words** The TDD cycle looks like this: 1. **Red** - write a test that is guaranteed to fail (the code does not exist yet or is wrong) 2. **Green** - write the minimal working code to make the test pass 3. **Refactor** - improve the code while keeping the tests green This cycle repeats continuously. --- ### **What TDD gives you** - **Clear understanding of requirements** - the system's behavior is formulated *before the code is written* - **Fewer bugs** - tests cover all cases from the very start - **Safe refactoring** - tests guarantee that the logic is not broken - **Clean architecture** - the code ends up modular and easy to test - **Confidence in the result** - the system works the way the tests describe --- ### **What this looks like in practice** Instead of writing a function and then thinking about how to test it, the developer does the opposite: > "First I formulate *what it should do*, then I write *how it does it*." --- ### **Summary** **TDD is a methodology in which tests define the behavior and design of the code.** It forces you to think through the result in advance and gives clear, verifiable correctness criteria at every step of development. ---For the reviewerNote to the moderator (optional)Visible only to the moderator. Helps review go faster.